In general, as a material for fluid-pressurizing vanes which are sliding parts of compressors, there have generally been used special cast irons, and high-carbon or high speed tool steels with excellent wear resistance. Also, carbon vanes are sometimes used for heavy-load compressors.
However, with development of compressors with higher performance and larger load-carrying capacity, it has been found that the special cast-iron vanes involve such a problem that they are poor in wear resistance. On the other hand, the high-carbon or high speed tool steel vanes possess excellent wear resistance as their hardness may be improved by thermal treatments, but they attack opposing parts and cause seizure because of their poor self-lubricating ability. Also, the carbon vanes have such a problem that they are too expensive.
Recently, sintered alloy vanes produced by sintering have partially received practical application. Such sintered alloy vane are composed, as disclosed in the Japanese Patent Gazette of laying-open No. 59-16952 for example, of a sintered iron-base alloy consisting of a matrix of a base metal of iron and hard particles such as carbides dispersed in the matrix. In such vanes, the mechanical strength of the matrix is ensured by increasing the theoretical relative density to not less than 92%, while the wear resistance is improved by dispersion of the hard particles with a diameter of not less than 5 .mu.m into the matrix. Also, such sintered alloy vanes have a further advantage such that they possess self-lubricating when oil is impregnated into their pores.
However, the above sintered iron-base alloy vanes attack opposing parts and cause a seizure in a manner similar to the aforesaid steel vanes because of their high hardness of a macro-structure including the dispersed hard particles, which results from high theoretical relative density of not less than 92%.